1. Field
The present application relates to semiconductor processing, and more particularly to controlling critical dimensions of structures formed on a wafer.
2. Related Art
In semiconductor processing, semiconductor devices/circuits are formed on a wafer by depositing and patterning layers of materials. In general, the features of the devices/circuits are formed onto the layers of deposited materials using a patterning process.
In a conventional patterning process, a photoresist layer is deposited on top of a film layer on which the features of the devices/circuits are to be formed. A photomask with a layout of the features of the devices/circuits is positioned over the photoresist, then exposed to light. A developing solution is used to dissolve the portions of the photoresist either exposed or not exposed to the light through the photomask. An etching system is then used to strip the portions of the film layer not protected by the photoresist. In this manner, the features on the photomask are formed as structures on the film layer.
Non-uniformities associated with the patterning process, however, can produce undesirable variations in the critical dimensions of the structures formed by the patterning process. For example, the resist development and conventional etching tools used in the patterning process, such as plasma dry etchers, typically produce non-uniform variations in the critical dimensions of structures from the center to edge of a wafer. Correcting for the non-uniform variations in conventional etching tools can be difficult.